Potential Converter Circuit

ABSTRACT

Embodiments of a potential converter circuit include a converter for converting a bipolar input signal to a unipolar output signal that only consumes current at a change of potential of the input signal.

This application claims priority to German Patent Application 10 2008012 809.0, which was filed Mar. 6, 2008 and is incorporated herein byreference.

TECHNICAL FIELD

Embodiments of the present invention relate to a potential convertercircuit, in particular, to a potential converter circuit for convertinga bipolar input signal to a unipolar output signal.

BACKGROUND

In semiconductor circuits comprising MOSFET transistors, the reliabilityrequirements limit a maximum occurring voltage across the gate oxide ofthe semiconductor to, for example, a value of approximately 3.6 volts(e.g., in the processing technology C7NP). That means a voltage betweengate and source or gate and drain, respectively, of a MOSFET transistorshould not have an amount of more than approximately 3.6 volts forensuring reliable operation of the transistor. Direct driving of thegate with the bipolar input voltage of, for example, +/−3 volts cancause destruction of the transistor.

In order to avoid a bipolar input voltage from being applied directly atthe input of the transistor, potential converter circuits are used.

SUMMARY OF THE INVENTION

According to embodiments, the present invention provides a potentialconverter circuit having a means for converting a bipolar input signalto a unipolar output signal that only consumes current at a change ofpotential of the input signal.

Since current is only consumed at a change of potential of the inputsignal, power will be consumed only in this case. Thus, the potentialconverter circuit can be operated in a highly power-efficient manner,since, contrary to conventional circuits, power is not consumedpermanently but only for the short period of the change of potential ofthe input signal.

With the potential converter circuit, a bipolar logic signal,comprising, for example, the voltage range of −V_(dd) to +V_(dd) andthus having a maximum potential difference of 2*V_(dd) can be convertedto a unipolar logic signal comprising, for example, the voltage range of0 volts to −V_(dd), and thus only having a maximum potential differenceof V_(dd). The converted unipolar logic signal allows reliable operationof the transistors in CMOS circuits, since only half the voltage swingof the bipolar input signal is applied to the transistors of the CMOScircuits, i.e., across the gate oxide of the transistors. Thus, it ispossible to operate CMOS circuits reliably and with little powerconsumption.

The reduced power consumption in comparison to conventional circuitslimits the process costs. Further, the lower power consumption allowsscaling of the circuit with the semiconductor technology. The potentialconverter circuit can also be advantageously used in smaller structuresizes that are smaller than usual, e.g., in C7NP technology.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the appended drawings, in which:

FIG. 1 is a circuit diagram of a potential converter circuit accordingto an embodiment of the invention;

FIG. 2 is a circuit diagram of a potential converter circuit accordingto a further embodiment of the invention;

FIG. 3 is a circuit diagram of a potential converter circuit accordingto a further embodiment of the invention; and

FIG. 4 is a circuit diagram of a potential converter circuit accordingto a further embodiment of the invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the following, embodiments of the potential converter circuit will bediscussed in detail with reference to the accompanying drawings FIGS. 1to 4.

With regard to the subsequent description of the embodiments of thepresent invention it should be noted that for simplicity reasons, thesame reference numbers are used in the whole description in thedifferent figures for functionally identical, or equal or functionallyequal, equivalent elements.

FIG. 1 shows a circuit diagram of a potential converter circuit 200according to an embodiment of the invention. A potential convertercircuit 200 for converting a bipolar input signal 202 to a unipolaroutput signal 203 can have a first switch 206 and a second switch 207.In this embodiment, the first switch 206 is connected between an input204 and an output 205 of the potential converter circuits 200 and has afirst switching capacitance 208. In this embodiment, a second switch 207is connected between the output 205 and a reference potential 213 of thepotential converter circuit 200 and has a second switching capacitance209. In this embodiment, the first switch 206 and the second switch 207are configured for charging and discharging the switching capacitances208, 209 of switches 206, 207 only at a change of potential of the inputsignal 202. For ensuring this mode of operation, the potential convertercircuit 200 has a control 210, which is implemented to control the firstswitch 206 by using a first control signal 211 and the second switch 207by using a second control signal 212. The control 210 generates the twocontrol signals 211, 212 in dependence on the input signal 202.

For generating the unipolar output signal 203 from the bipolar inputsignal 202, the control 210 can control, for example, closing of thefirst switch 206 with the first control signal 211 at a positive signalvalue of the input signal 202, and opening of the second switch 207 withthe second control signal 212, and control opening of the first switch206 with the first control signal 211 at a negative signal value of theinput signal 202, and control closing of the second switch 207 with thesecond control signal 212. This means that at a positive signal value ofthe input signal 202, the first switch 206 is closed and the secondswitch 207 is opened, such that the positive potential or the positivesignal value, respectively, of the input signal 202 is switched throughto the output 205, such that the output signal 203 has a positive signalvalue. On the other hand, at a negative signal value of the input signal202, the first switch 206 is opened and the second switch 207 is closed,such that the reference potential 213 is applied at the output 205, forexample, ground or zero volts, respectively. This corresponds to a modeof operation of the potential converter circuit 200 according to theillustration in FIG. 1. The output signal 203 is a unipolar signal withthe positive potential of the input signal 202 and the referencepotential 213.

On the other hand, the control 210 can also control, for example,opening of the first switch 206 with the first control signal 211 at apositive signal value of the input signal 202, and control closing ofthe second switch 207 with the second control signal 212, and, at anegative signal value of the input signal 202, control closing of thefirst switch 206 with the first control signal 211, and control openingof the second switch 207 with the second control signal 212. In thiscase, at a positive signal value of the input signal 202, the firstswitch 206 is opened and the second switch 207 is closed. Thus, thecommon reference potential 213 is applied to the output 205. At anegative signal value of the input signal 202, however, the first switch206 is closed and the second switch 207 is opened, such that thenegative signal value of the input signal 202 can be connected freely tothe output 205. Thus, the output signal 203 has the inverse waveformaccording to the illustration in FIG. 1, this means a change of negativepotential, for example, −3 volts, and common potential, for example, 0volts.

The control signals 211, 212 of the control 210 can, for example, bevoltages. The first switch 206 and the second switch 207 can, forexample, be MOSFET transistors, such that the control signals 211, 212are, for example, the control voltages of the MOSFET transistors appliedbetween gate and source or gate and drain. The MOSFET transistors can,for example, be transistors of the same type, they can, for example, ben-channel MOSFET transistors or p-channel MOSFET transistors. They canbe transistors of the enhancement type or of the depletion type. Forexample, the MOSFET transistors can be produced in C7NP semiconductortechnology. An implementation of the first switch 206 and the secondswitch 207 as MOSFET transistors will be described in more detail in thetwo following embodiments according to FIGS. 2 and 3.

Generally, the potential converter circuits 200, 100 can also be seen asrectifier circuits, since the same convert a bipolar input signal 202,102, to a unipolar output signal 203, 103. The input signal 202, 102can, for example, also be an alternating current or an alternatingvoltage, which can, for example, be a sinusoidal signal. The potentialconverter circuit 200, 100 blocks when the positive signal portion isapplied, and passes only the negative signal portion, or blocks when thenegative signal portion is applied and passes only the positive signalportion. This is the mode of operation of a rectifier.

FIG. 2 shows a circuit diagram of a potential converter circuit 300according to a further embodiment of the invention. The potentialconverter circuit 300 has an input 301, an output 302, a first MOSFETtransistor 303 and a second MOSFET transistor 304. The first MOSFETtransistor 303 has a source terminal 331, a drain terminal 333, a gateterminal 332 and a bulk terminal 334. The second MOSFET transistor 304has a source terminal 341, a drain terminal 343, a gate terminal 342 anda bulk terminal 344. Both transistors 303, 304 are connected to theinput 301, the output 302, a reference potential 305 and to each othersuch that the source terminal 331 of the first MOSFET transistor 303 isconnected to the output 302, the drain terminal 333 of the first MOSFETtransistor 303 is connected to the input 301, and that the gate terminal332 of the first MOSFET transistor 303 is connected to the referencepotential 305. Further, the source terminal 341 of the second MOSFETtransistor 304 is connected to the reference potential 305, the drainterminal 343 of the second MOSFET transistor 304 is connected to theoutput 302, and the gate terminal 342 of the second MOSFET transistor304 is connected to the input 301. The bulk terminals 334, 344 of thetwo transistors 303, 304 are connected to the output 302 of thepotential converter circuit 300 to avoid stress due to a higher voltage.

Thus, the circuit structure of the potential converter circuit 300connects the first MOSFET transistor 303 to a common gate circuit. Agate circuit is one of three basic circuits of field effect transistors.Here, the drain terminal 333 of the first transistor 303 serves as input301, the source terminal 331 of the first transistor 303 serves asoutput 302, and the gate terminal 332 of the first transistor 303 ascommon input 301 and output 302. Since the gate terminal 332 of thetransistor 303 is connected to a reference potential 305, to which theinput signal 321 at the input 301 relates, and to which the outputsignal 322 at the output 302 relates, the gate terminal 332 is commonwith regard to the input 301 and the output 302. The reference potential305 can represent, for example, a ground potential or a common groundpotential, respectively. In the waveforms according to FIG. 2, thereference potential 305 corresponds to the zero line. The input signal321 is a bipolar input signal, the same can have, for example, thepositive potential +V_(in) and the negative potential −V_(in). Theoutput signal 322 is a unipolar output signal, the same has a firstsignal value corresponding to the reference potential 305, and the samehas a second signal value that can, for example, be −V_(in) or +V_(in),i.e., corresponds to the negative or positive potential of the inputsignal 321.

The second MOSFET transistor 304 is connected via a common-sourcecircuit. A source circuit is a further one of three basic circuits offield effect transistors. In the source circuit, the gate terminal 342of the second transistor 304 serves as input 301 and the drain terminal343 of the second transistor 304 serves as output 302, and the sourceterminal 341 of the second transistor 304 is both input 301 and output302. The source terminal 341 of the second transistor 304 is connectedto the reference potential 305, to which both the input 301 and theoutput 302 are related. Thus, the source terminal 341 is implemented ascommon-source circuit with regard to input 301 and output 302.

The potential converter circuit 300 comprises a first metal-oxide fieldeffect transistor 303, which is implemented as an n-channel MOSFETtransistor in this embodiment and is operated in a gate circuit, and asecond metal-oxide field effect transistor 304, which is alsoimplemented as an n-channel MOSFET transistor in this embodiment, and isoperated in a source circuit. Both transistors 303, 304 can be operatedin the enhancement mode. The gate terminal 332 of the first transistor303 and the source terminal 341 of the second transistor 304 are on areference potential 305, which can, for example, be a common groundpotential. The source terminal 331 of the first transistor 303 and thedrain terminal 343 of the second transistor 304 are connected to theoutput 302. The drain terminal 333 of the first transistor 303 and thegate terminal 342 of the second transistor 304 are connected to theinput 301.

The potential converter circuit 300 converts a bipolar input signal 321to a unipolar output signal 322. If, for example, the positive portion+Vi_(in) of the input signal 321 is applied to the input 301, thepotential +V_(in) is also applied to the drain terminal 333 of the firsttransistor 303 and to the gate terminal 342 of the second transistor304. In this embodiment, the reference potential 305 corresponds to acommon ground, i.e., it has a potential value of zero. Thus, thepotential value 0 is also applied to the source terminal 341 of thesecond transistor 304 and to the gate terminal 332 of the firsttransistor 303. Thus, the voltage between gate 342 and source 341 of thesecond transistor 304 corresponds to the input potential +V_(in). Sincethe input potential +V_(in) is higher than a threshold voltage V_(th) ofthe transistors 303, 304 in the common mode of operation of thepotential converter circuit 300, this means that the second transistor304 is conductive. Thus, the potential 0 of the source input 341 of thesecond transistor 304 is switched to the drain terminal 343 of thesecond transistor 304 and is applied at the same time to the output 302of the potential converter circuit 300. Additionally, the potential 0 ofthe source terminal 341 of the second transistor 304, which isconductive, is also applied to the source terminal 331 of the firsttransistor 303 as well as to the bulk terminal 334 of the firsttransistor 303 and to the bulk terminal 344 of the second transistor304. Thus, the voltage between the gate terminal 332 of the firsttransistor 303 and the source terminal 331 of the first transistor 303equals zero, and is thus smaller than a threshold voltage V_(th), whichmeans that the first transistor 303 is non-conductive. The potential+V_(in) applied to the drain terminal 333 of the first transistor 303 isnot switched to the output 302. The output 302 has the potential zero.

If the negative portion of the input signal 321, for example, with thepotential −V_(in) is applied to the input 301, then the potential−V_(in) is also applied to the drain terminal 333 of the firsttransistor 303 as well as to the gate terminal 342 of the secondtransistor 304. The reference potential 305, which means the potentialzero is further applied to the source terminal 341 of the secondtransistor 304 and to the gate terminal 332 of the first transistor 303.The voltage between gate 342 of the second transistor 304 and source 341of the second transistor 304 is −V_(in), and is thus smaller than thethreshold voltage V_(th) of the second transistor 304. This means thesecond transistor 304 is non-conductive at negative potentials −V_(in)to the input 301. If the potential zero is applied to the gate terminal332 of the first transistor 303 and the negative potential −V_(in) atthe drain terminal 333 of the first transistor 303, then the potentialof the gate terminal 332 is positive compared to the drain terminal 333,the voltage between gate 332 and drain 333 of the first transistor 303corresponds thus to +V_(in), i.e., for example, 3 volts and is thushigher than the threshold voltage V_(th). In common MOSFET transistors,threshold voltages V_(th) can, for example, be in the range of about 0.7to 0.2 volts. At a voltage between gate 332 and drain 333 of the firsttransistor 303 of V_(in), which is higher than the threshold voltage,the first transistor 303 is conductive. The potential −V_(in) of thedrain terminal 333 is switched through to the source terminal 331 of thefirst transistor 303 and thus also to the output 302 of the potentialconverter circuit 300. The potential of the drain terminal 333 of thefirst transistor 303 is also switched through to the bulk terminal 334of the first transistor 303, to the drain terminal 343 of the secondtransistor 304 and to the bulk terminal 344 of the second transistor304. The voltage between gate 332 and source 331 of the first transistor303 corresponds also to +V_(in) and is thus also higher than thethreshold voltage V_(th) of the first transistor 303. The transistor 303remains in the conductive state.

Due to the connectivity of the potential converter circuit 300, at apositive input voltage, which is higher than the threshold voltageV_(th), the first transistor 303 is non-conductive (potential of gatecompared to drain is negative) and the second transistor 304 isconductive (potential of gate compared to source is positive) such thatthe reference potential 305 is switched to the output 302. At a negativeinput signal 321, the first transistor 303 is conductive (potential ofgate compared to drain is positive) and the second transistor 304 isnon-conductive (potential of gate compared to source is negative), suchthat the negative input potential is switched through from the input 301to the output 302. A negative unipolar output signal 322 is generatedfrom a bipolar input signal 321.

According to its mode of operation, the first transistor 303 correspondsto the first switch 206 according to FIG. 1, and according to its modeof operation, the second transistor 304 corresponds to the second switch207 according to FIG. 1.

FIG. 3 shows a circuit diagram of a potential converter circuit 400according to a further embodiment of the invention. The potentialconverter circuit 400 has the same components and the same connectivityas the potential converter circuit 300, the bulk terminals 434, 444 arealso connected to the output 402. The difference is that the twotransistors 403, 404 are implemented as p-channel metal-oxide fieldeffect transistors. This results in a different functionality, whichwill be described below.

In p-channel MOSFET transmitters, the transistor is conductive when thepotential difference of gate terminal and source terminal becomessmaller than a negative threshold voltage, and the transistor isnon-conductive when the potential difference of gate terminal and sourceterminal becomes higher than the negative threshold voltage. In abipolar input signal 421, applied to the input 401, and having the twopolarities +V_(in) and −V_(in), the following behavior results: If thepositive potential +V_(in) is applied to the input 401, the same is alsoapplied to the drain terminal 433 of the first transistor 403 and to thegate terminal 442 of the second transistor 404. A common potential 405,for example, with the potential 0, is applied to the source terminal 441of the second transistor 404 and to the gate terminal 432 of the firsttransistor 403. The potential difference between gate terminal 442 ofthe second transistor 404 and source terminal 441 of the secondtransistor 404 corresponds then to +V_(in), is thus higher than anegative threshold voltage −V_(th), such that the second transistor 404is non-conductive. At the first transistor 403, the potential differencebetween gate terminal 432 and drain terminal 433 is equal to thenegative input potential, i.e., −V_(in). At common values of the inputpotential V_(in) of approximately 3 volts, where the potential convertercircuit 400 can be operated, and at common threshold voltages ofapproximately 0.7 to 0.2 volts, which MOSFET transistors 403, 404 have,the potential difference between gate 432 and drain 433 of the firsttransistor 403 is smaller than a negative threshold voltage −V_(th),such that the first transistor 403 is conductive. The potential of drainterminal 433 is switched to the source terminal 431 of the firsttransistor 403 and is also applied to the output 402 of the potentialconverter circuit 400. The potential +V_(in) of the source terminal 431of the first transistor 403 is also applied to the bulk terminal 434 ofthe first transistor 403, to the drain terminal 443 of the secondtransistor 404 and to the bulk terminal 444 of the second transistor404. The potential difference between gate terminal 442 of the secondtransistor 404 and drain terminal 443 of the second transistor 404 isthus equal to zero, and thus still higher than the negative thresholdvoltage −V_(th), such that the second transistor 404 is stillnon-conductive.

This means that at a positive potential of the input signal 421, theoutput signal 422 at the output 402 also has positive potential.

If the negative potential −V_(in) of the input signal 421 is applied tothe input 401, the same will also be applied to the drain terminal 433of the first transistor 403 and to the gate terminal 442 of the secondtransistor 404. The potential difference between the gate terminal 442of the second transistor 404 and source terminal 441 of the secondtransistor 404 is thus equal to −V_(in), which means it is smaller thanthe negative threshold voltage −V_(th), such that the second transistor404 is conductive. Thus, the second transistor 404 switches thereference potential 405 or the potential 0, respectively, to the drainterminal 443 of the second transistor 404 and to the output 402. Thepotential 0 is also switched to the source terminal 431 of the firsttransistor 403, to the bulk terminal 434 of the first transistor 403 andto the bulk terminal 444 of the second transistor 404. Thus, thepotential difference between the gate terminal 432 and source terminal431 of the first transistor 403 equals zero, is thus higher than thenegative threshold voltage −V_(th), such that the first transistor 403remains non-conductive. This means a negative potential of the inputsignal 421 does not reach the output 402, due to the non-conductivestate of the first transistor 403.

The potential converter circuit 400 is implemented such that a positivepotential of the input signal 421 is switched to the output 402, and thefirst transistor 403 is non-conductive at a negative potential of theinput signal 421, and at the same time the second transistor 404 isconductive to switch the reference potential 405 to the output 402.Thus, the first transistor 403 corresponds to the first switch 206according to FIG. 1 in its mode of operation, and the second transistor404 corresponds to the second switch 207 according to FIG. 1 in its modeof operation. Either the potential of the input 401 or the potential ofthe reference potential 405 is switched to the output 402. One of thetransistors 403, 404 each is conductive, while the other one isnon-conductive. The switching process takes place reliably when thepotential at the input is higher than the positive threshold voltage orsmaller than the negative threshold voltage, respectively, wherein thethreshold voltages correspond to the threshold voltages of metal-oxidefield effect transistors.

The transistors 403, 404 can, for example, be of the enhancement type,the same can be produced, for example, in a C7NP semiconductortechnology. In the potential converter circuits 300, 400 of theembodiments according to FIG. 2 and FIG. 3, current flow only occurs atthe switching processes for reloading the gate capacities of thetransistors. Thus, power is only consumed in the switching process forcharging or discharging the capacitances. Further, it has to be notedthat the highest amount of the potential across the gate oxide of bothtransistors 303, 403 or 304, 404, respectively, does not exceed thepotential V_(in). In no state, in which the circuit 300, 400 is, adouble amount is applied across the gate oxide of one of thetransistors, i.e., 2*V_(in). Thus, the transistors 303, 403 or 304, 404,respectively can operate in an approved voltage range. Further, thepotential converter circuit 300, 400 can be implemented on asemiconductor substrate in a very space-saving manner, since only twotransistors are necessary for realizing the circuit. This has theadvantage that the switching velocity is increased compared to commoncircuits necessitating a larger number of transistors.

FIG. 4 shows a circuit diagram of a potential converter circuit 100according to a further embodiment of the invention. In this embodiment,the potential converter circuit 100 comprises a means 101 for convertinga bipolar input signal 102 to a unipolar output signal 103, which onlyconsumes current at a change of potential of the input signal 102. Thismeans, if the bipolar input signal 102 changes, for example, from apositive voltage to a negative voltage or vice versa, current and thuspower is consumed in the means 101 for converting the bipolar inputsignal 102 to the unipolar output signal 103.

The means 101 can have, for example, two MOSFET transistors of the sametype, whose capacitances are only charged and discharged at a change ofpotential of the input signal 102. For example, both of the two MOSFETtransistors can be n-channel or p-channel MOSFET transistors. The MOSFETtransistors can be of the enhancement type or of the depletion type. Themeans 101 can also have other types of transistors, for example, JFETtransistors (JFET=junction field effect transistor), IGBT transistors(IGBT=insulated gate bipolar transistor), TFT transistors (TFT=thin filmtransistor), photo transistors or others.

In the following, embodiments of the present invention will be describedagain in other words. For reducing the supply voltage in highly linearCMOS circuits and for excluding the usage of DC blocking capacitors, thegate terminals of the switching transistors are operated in highlylinear CMOS circuits with bipolar voltage. Since the control circuitshould operate with standard logic potentials, a potential converter isnecessary for converting a unipolar to a bipolar signal. The inventivepotential converter converts a bipolar to a unipolar signal and can beused in the feedback path of the transistor driver circuit. Since thereliability requirement limits a maximum voltage across the gate oxideto, for example, 3.6 volts in the C7NP technology, the direct approachallows no switching of +/−3 volts. Recently, an ohmic potentialconverter has been used with a common gate transistor. However, thisapproach consumes current that can be provided, for example, by theembedded charging pump, and necessitates a large area. A second approachwith capacitively coupled logic has also been tested, but has been givenup because the circuit was in an undefined state after applying thesupply voltage. The inventive solution allows the operation of standardlogic cells without drawing additional current. It needs remarkablylittle area on the chip and satisfies the reliability requirements.Embodiments of the invention represent a combination of MOSFETtransistor switches in a common gate and a common source circuit forperforming the potential conversion. Embodiments of the inventionrepresent a reliable low-power potential converter. The potentialconverter circuit according to embodiments of the invention converts abipolar logic signal, i.e., a signal ranging from, for example, −V_(dd)to +V_(dd) and thus including a voltage range of 2*V_(dd), to a unipolarlogic signal, which ranges, for example, from 0 volts to −V_(dd),without providing the gate oxide of the transistor with more than halfthe voltage swing of the input signal. This has the effect of increasingthe reliability of the transistors in CMOS circuits.

In embodiments of the invention, the potential converter circuitcomprises a first NMOS transistor Q1 in a common gate circuit and asecond NMOS transistor in a common source circuit. Both transistorsoperate in the enhancement mode. The gate of the transistor Q1 and thesource terminal of the transistor Q2 are on a common ground potential,the source terminal of Q1 and the drain terminal of Q2 are connected tothe output. The drain terminal of Q1 and the gate of Q2 are connected tothe input. If the same is positive with regard to ground, the inputvoltage +V_(in) is applied to the input. The transistor Q2 becomesconductive when the input voltage V_(in) is higher than a thresholdvoltage V_(th) of the respective transistor, such that Q2 provides acurrent path with low resistance from the output to ground. Q1 becomesnon-conductive, since its gate potential is negative both with regard tosource and to drain. The highest potential with regard to the gateterminals is V_(gd). Q1=V_(gs), Q2=V_(in). At a negative voltage−V_(in), Q1 becomes conductive for V_(in) larger V_(th), for providing acurrent path with low resistance at the input. The highest potentialacross the gate oxide of both transistors does not exceed V_(in). Theonly current necessitated by the circuit is the one for reloading thegate capacities during the switching process. A similar circuit can bedesigned for positive logic by using two PMOS transistors. In this case,the bipolar input logic signal is converted from +V_(dd)/−V_(dd) toV_(dd)/0 volts.

While this invention has been described in terms of several advantageousembodiments, there are alterations, permutations, and equivalents whichfall within the scope of this invention. It should also be noted thatthere are many alternative ways of implementing the methods andcompositions of the present invention. It is therefore intended that thefollowing appended claims be interpreted as including all suchalterations, permutations, and equivalents that fall within the truespirit and scope of the present invention.

1. A potential converter circuit for converting a bipolar input signalto a unipolar output signal, the circuit comprising: a first switchcoupled between an input and an output and comprising a first switchingcapacitance; and a second switch coupled between the output and areference potential and comprising a second switching capacitance,wherein the first switch and the second switch are configured forcharging and discharging the switching capacitances of the switches onlyat a change of potential of the input signal.
 2. The potential convertercircuit according to claim 1, further comprising a control, wherein thecontrol is configured for controlling the first switch using a firstcontrol signal and the second switch using a second control signal,wherein the first and second control signals are derived from the inputsignal.
 3. The potential converter circuit according to claim 2, whereinthe control is configured for closing or opening the first switch at apositive signal value of the input signal using the first controlsignal, and for opening or closing the second switch using the secondcontrol signal, and for opening or closing the first switch at anegative signal value of the input signal using the first controlsignal, and for closing or opening the second switch using the secondcontrol signal.
 4. The potential converter circuit according to claim 1,wherein the first switch and the second switch comprise MOSFETtransistors of the same type.
 5. The potential converter circuitaccording to claim 4, wherein the first switch is controlled by a firstcontrol signal and the second switch is controlled by a second controlsignal, the first and second control signals being voltages between gateand source or between gate and drain of the MOSFET transistors.
 6. Thepotential converter circuit according to claim 4, wherein the firstswitch and the second switch comprise n-channel MOSFET transistors orp-channel MOSFET transistors.
 7. The potential converter circuitaccording to claim 4, wherein the MOSFET transistors are enhancementtype transistors.
 8. The potential converter circuit according to claim4, wherein the MOSFET transistors are implemented in a C7NP technology.9. A potential converter circuit for converting a bipolar input signalto a unipolar output signal, the circuit comprising: an input; anoutput; a first MOSFET transistor comprising a source terminal connectedto the output, a drain terminal connected to the input, and a gateterminal connected to a reference potential; and a second MOSFETtransistor comprising a source terminal connected to the referencepotential, a drain terminal connected to the output, and a gate terminalconnected to the input.
 10. The potential converter circuit according toclaim 9, wherein the first MOSFET transistor and the second MOSFETtransistor are n-channel transistors.
 11. The potential convertercircuit according to claim 9, wherein the first MOSFET transistor andthe second MOSFET transistor are p-channel transistors.
 12. Thepotential converter circuit according to claim 9, wherein the first andsecond MOSFET transistors are enhancement type transistors.
 13. Thepotential converter circuit according to claim 9, wherein a bulkterminal of the first MOSFET transistor and a bulk terminal of thesecond MOSFET transistor are connected to the output.
 14. The potentialconverter circuit according to claim 9, wherein the input carries abipolar logic signal.
 15. The potential converter circuit according toclaim 14, wherein the bipolar logic signal describes two logic statesthat are predetermined by a positive supply voltage and a negativesupply voltage.
 16. The potential converter circuit according to claim9, wherein the output carries a unipolar logic signal.
 17. The potentialconverter circuit according to claim 16, wherein the unipolar logicsignal describes two logic states that are predetermined by a negativeor positive supply voltage, respectively, and a reference potential. 18.The potential converter circuit according to claim 9, wherein the firstMOSFET transistor is connected in a gate circuit.
 19. The potentialconverter circuit according to claim 9, wherein the second MOSFETtransistor is connected in a source circuit.
 20. The potential convertercircuit according to claim 9, wherein the reference potential is aground potential.
 21. The potential converter circuit according to claim9, wherein the MOSFET transistors are implemented in a C7NP technology.22. A potential converter circuit, comprising: a converter forconverting a bipolar input signal to a unipolar output signal that onlyconsumes current at a change of potential of the input signal.
 23. Thepotential converter circuit according to claim 22, wherein the convertercomprises two MOSFET transistors of the same type, whose capacitancesare only charged or discharged at a change of potential.